When the diaphragm contracts, it flattens downward, which increases the volume of the thoracic cavity and decreases the pressure, allowing air to rush into the lungs.

Pulmonary surfactant reduces surface tension within the alveoli, preventing them from sticking together and collapsing during expiration.

Approximately 98-99% of oxygen in the blood is carried by hemoglobin inside red blood cells.

The pleura is a double-layered serous membrane that surrounds each lung, providing lubrication to reduce friction during breathing.

The respiratory centers located in the medulla oblongata and pons of the brainstem control the rate and depth of respiration.

The majority of carbon dioxide (about 70%) is transported in the blood in the form of bicarbonate ions dissolved in the plasma.

Tidal volume is the amount of air inhaled or exhaled per breath during normal, resting ventilation.

The trachea is supported by C-shaped hyaline cartilage rings that keep the airway open during respiration.

Chemoreceptors are highly sensitive to rising levels of carbon dioxide (and subsequent drop in pH), which triggers the brain to increase breathing rate to remove CO2.

The larynx contains the vocal cords and is known as the voice box.

The epiglottis is a flap of cartilage that covers the glottis during swallowing to prevent food or liquid from entering the respiratory pathway.

Pneumothorax is the collapse of a lung due to the entry of air into the pleural space, which disrupts the negative pressure required for lung inflation.

Forced expiration involves the contraction of internal intercostal muscles, which pulls the rib cage downward and inward, decreasing thoracic volume.

Oxygen diffuses from the blood into the tissues because the PO2 in the tissues is lower than that in the systemic arterial blood.

Residual volume is the air remaining in the lungs after maximal expiration and cannot be measured by simple spirometry.

Bronchioles lack the cartilage rings found in the trachea and bronchi, consisting mainly of smooth muscle instead.

Carbon monoxide binds to hemoglobin with an affinity approximately 200-250 times greater than that of oxygen, forming carboxyhemoglobin.

Increased H+ concentration (lower pH) decreases hemoglobin's affinity for oxygen, causing a rightward shift in the dissociation curve (Bohr effect).

The alveolar-capillary membrane provides a thin barrier that allows for the rapid diffusion of gases between the alveoli and the pulmonary capillaries.